Electric motors that comprise an internal stator and an external rotor are usually equipped with magnets in the form of annular permanent magnets. The external rotor comprises a rotor housing implemented in the manner of a hollow cylinder or a cup. The internal stator is received in the interior of the rotor housing, thus in a manner predominantly surrounded by the rotor housing, so that the external rotor is rotatable around the internal stator. An annularly shaped permanent magnet has an outer contour whose shape is adapted to the inner surface of the rotor housing and can thus easily be fastened thereon.